Anti-migration stent

ABSTRACT

An illustrative stent includes an elongated tubular member comprising at least one strut or filament forming a tubular wall having a plurality of cells extending through a thickness of the tubular wall. The elongated tubular member may be configured to move between a radially collapsed configuration and a radially expanded configuration. A coating is disposed on the elongated tubular member and spanning the plurality of cells. The coating forms a pocket within at least some of the cells of the plurality of cells and extends radially inward of the tubular wall to define a void. In some instances, a partition or wall is positioned within at least some of the pockets and transects the void.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.17/125,116, filed Dec. 17, 2020, which claims the benefit of andpriority to U.S. Provisional Patent Application Ser. No. 62/960,470,filed on Jan. 13, 2020, the disclosures of which are incorporated hereinby reference.

TECHNICAL FIELD

The present disclosure pertains to medical devices, methods formanufacturing medical devices, and uses thereof. More particularly, thepresent disclosure pertains to an anti-migration stent for implantationin a body lumen, and associated methods.

BACKGROUND

Implantable stents are devices that are placed in a body lumen, such asthe esophageal tract, the gastrointestinal tract (including theintestine, stomach and the colon), tracheobronchial tract, urinarytract, biliary tract, vascular system, etc. to provide support and tomaintain the body lumen open. These stents are manufactured by any oneof a variety of different manufacturing methods and may be usedaccording to any one of a variety of methods. Of the known stents,delivery systems, and methods, each has certain advantages anddisadvantages. For example, in some stents, the compressible andflexible properties that assist in stent delivery may also result in astent that has a tendency to migrate from its originally deployedposition. For example, stents that are designed to be positioned in theesophageal or gastrointestinal tract may have a tendency to migrate dueto peristalsis (i.e., the involuntary constriction and relaxation of themuscles of the esophagus, intestine, and colon which push the contentsof the canal therethrough). Thus, there is an ongoing need to providealternative stents having anti-migration features and associateddelivery systems as well as alternative methods for manufacturing andusing stents having anti-migration features and associated deliverysystems.

BRIEF SUMMARY

This disclosure provides design, material, manufacturing method, and usealternatives for medical devices. An example medical device may includea stent.

In a first example, a stent may comprise an elongated tubular membercomprising at least one strut forming a tubular wall having a pluralityof cells extending through a thickness of the tubular wall, theelongated tubular member configured to move between a radially collapsedconfiguration and a radially expanded configuration, a coating disposedon the elongated tubular member and spanning the plurality of cells, thecoating forming a pocket within at least some of the plurality of cellsand extending radially inward of the tubular wall to define a void, anda partition positioned within at least some of the pockets, eachpartition extending radially outward from a bottom surface of the pocketand transecting the void.

Alternatively or additionally to any of the examples above, in anotherexample, at least some of the partitions may extend generallyperpendicular to a central longitudinal axis of the elongated tubularmember.

Alternatively or additionally to any of the examples above, in anotherexample, at least some of the partitions may extend generally parallelto a central longitudinal axis of the elongated tubular member.

Alternatively or additionally to any of the examples above, in anotherexample, at least some of the partitions may extend at an oblique anglerelative to a central longitudinal axis of the elongated tubular member.

Alternatively or additionally to any of the examples above, in anotherexample, a height of the partitions may be approximately equal to aheight of the at least one strut having the coating disposed thereon.

Alternatively or additionally to any of the examples above, in anotherexample, the at least one strut may form a plurality of cross-overpoints.

Alternatively or additionally to any of the examples above, in anotherexample, at least some of the partitions may extend between adjacentcross-over points.

Alternatively or additionally to any of the examples above, in anotherexample, at least some of the partitions may extend from a first side ofthe pocket to a second side of the pocket in which it is positioned.

Alternatively or additionally to any of the examples above, in anotherexample, at least one pocket may include two or more partitions.

Alternatively or additionally to any of the examples above, in anotherexample, the coating may define an entirety of a surface of a lumenextending longitudinally through the stent.

Alternatively or additionally to any of the examples above, in anotherexample, at least some of the pockets may include an aperture formedtherethrough.

Alternatively or additionally to any of the examples above, in anotherexample, the coating and the partitions may be formed as a singlemonolithic structure.

Alternatively or additionally to any of the examples above, in anotherexample, the coating may be disposed over an inner surface and/or anouter surface of the elongated tubular member.

In another example, a stent may comprise an elongated tubular membercomprising at least one strut forming a tubular wall having a pluralityof cells extending through a thickness of the tubular wall, theelongated tubular member configured to move between a radially collapsedconfiguration and a radially expanded configuration and a coatingdisposed on the elongated tubular member and spanning the plurality ofcells, the coating forming a pocket within at least some of theplurality of cells and extending radially inward of the tubular wall todefine a void. The pockets may be pyramidal shaped, with four convergingside walls and a base wall intersecting each of the four converging sidewalls.

Alternatively or additionally to any of the examples above, in anotherexample, the stent may further comprise a partition positioned within atleast some of the pockets, each partition extending radially outwardfrom the base surface of the pocket and transecting the void.

In another example, a stent may comprise an elongated tubular membercomprising at least one interwoven filament forming a tubular wall, theat least one interwoven filament forming a plurality of cross-overpoints and defining a plurality of cells therebetween extending througha thickness of the tubular wall, the elongated tubular member configuredto move between a radially collapsed configuration and a radiallyexpanded configuration, a polymer coating disposed on the elongatedtubular member, the coating forming a pocket within at least some of theplurality of cells and extending radially inward of the tubular wall todefine a void, and a partition formed within at least some of thepockets, each partition extending radially outward from a bottom surfaceof the pocket and transecting the void between opposing cross-overpoints of the at least one strut forming the cell in which the pocket ispositioned.

Alternatively or additionally to any of the examples above, in anotherexample, at least some of the partitions may extend generallyperpendicular to a central longitudinal axis of the elongated tubularmember.

Alternatively or additionally to any of the examples above, in anotherexample, at least some of the partitions may extend generally parallelto a central longitudinal axis of the elongated tubular member.

Alternatively or additionally to any of the examples above, in anotherexample, the coating may define an entirety of a surface of a lumenextending longitudinally through the stent.

Alternatively or additionally to any of the examples above, in anotherexample, the coating and the partitions may be formed as a singlemonolithic structure.

Alternatively or additionally to any of the examples above, in anotherexample, a radial outermost extent of the partitions may be locatedflush with or radially inward of an outer surface of the tubular wall.

The above summary of some embodiments is not intended to describe eachdisclosed embodiment or every implementation of the present disclosure.The Figures, and Detailed Description, which follow, more particularlyexemplify these embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments in connection withthe accompanying drawings, in which:

FIG. 1 is a side view of an illustrative stent having an anti-migrationsystem.

FIG. 2A is a partial perspective view of the illustrative stent of FIG.1 .

FIG. 2B is a partial side view of the illustrative stent of FIG. 1 .

FIG. 3 is a cross-sectional view of the illustrative stent of FIG. 1disposed within a body lumen.

FIG. 3A is a cross-sectional view of an alternative variation of thestent of FIG. 1 disposed within a body lumen.

FIG. 4 is a side view of another illustrative stent having ananti-migration system.

FIG. 5A is a partial perspective view of another illustrative stent.

FIG. 5B is a partial side view of the illustrative stent of FIG. 4A.

FIG. 6 is a cross-sectional view of the illustrative stent of FIG. 4disposed within a body lumen.

FIG. 6A is a cross-sectional view of an alternative variation of thestent of FIG. 4 disposed within a body lumen.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit aspects of theinvention to the particular embodiments described. On the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the scope of the invention.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied,unless a different definition is given in the claims or elsewhere inthis specification.

All numeric values are herein assumed to be modified by the term“about”, whether or not explicitly indicated. The term “about” generallyrefers to a range of numbers that one of skill in the art would considerequivalent to the recited value (i.e., having the same function orresult). In many instances, the term “about” may be indicative asincluding numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numberswithin that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4,and 5).

Although some suitable dimensions ranges and/or values pertaining tovarious components, features and/or specifications are disclosed, one ofskill in the art, incited by the present disclosure, would understanddesired dimensions, ranges and/or values may deviate from thoseexpressly disclosed.

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” include plural referents unless the contentclearly dictates otherwise. As used in this specification and theappended claims, the term “or” is generally employed in its senseincluding “and/or” unless the content clearly dictates otherwise.

The following detailed description should be read with reference to thedrawings in which similar elements in different drawings are numberedthe same. The detailed description and the drawings, which are notnecessarily to scale, depict illustrative embodiments and are notintended to limit the scope of the invention. The illustrativeembodiments depicted are intended only as exemplary. Selected featuresof any illustrative embodiment may be incorporated into an additionalembodiment unless clearly stated to the contrary.

In some instances, it may be desirable to provide an endoluminalimplant, or stent, that can deliver luminal patency in a patient with anesophageal stricture or other medical condition. Such stents may be usedin patients experiencing dysphagia, sometimes due to esophageal cancer.An esophageal stent may allow a patient to maintain nutrition via oralintake during cancer treatment or palliation periods. However, a commoncomplication of gastrointestinal (GI) stents is stent migration due tothe peristaltic motion subjected to the stent. Uncoated stents allow thegranulation tissue of the esophagus to encompass the stent andeffectively grip the wires of the stent. While this tissue ingrowth mayhelp prevent the migration of the stent, the stent may be difficult toremove. It may be desirable to provide a stent that can deliver luminalpatency while minimizing migration of the stent and allowing for removalof the stent. While the embodiments disclosed herein are discussed withreference to esophageal stents, it is contemplated that the stentsdescribed herein may be used and sized for use in other locations suchas, but not limited to: bodily tissue, bodily organs, vascular lumens,non-vascular lumens and combinations thereof, such as, but not limitedto, in the coronary or peripheral vasculature, trachea, bronchi, colon,small intestine, biliary tract, urinary tract, prostate, brain, stomachand the like.

FIG. 1 illustrates a side view of an illustrative endoluminal implant10, such as, but not limited to, a stent. In some instances, the stent10 may be formed from an elongated tubular member 12. While the stent 10is described as generally tubular, it is contemplated that the stent 10may take any cross-sectional shape desired. The stent 10 may have afirst, or proximal end 14, a second, or distal end 16, and anintermediate region 18 disposed between the first end 14 and the secondend 16. The stent 10 may include a lumen 32 extending from a firstopening adjacent the first end 14 to a second opening adjacent to thesecond end 16 to allow for the passage of food, fluids, etc.

The stent 10 may be expandable from a first radially collapsedconfiguration (not explicitly shown) to a second radially expandedconfiguration. In some cases, the stent may be deployed to aconfiguration between the collapsed configuration and a fully expandedconfiguration. The stent 10 may be structured to extend across astricture and to apply a radially outward pressure to the stricture in alumen to open the lumen and allow for the passage of foods, fluids, air,etc.

In some embodiments, the proximal end 14 of the stent 10 may include aplurality of loops 38. The loops 38 may be configured to receive aretrieval tether or suture (not explicitly shown) interwoventherethrough, or otherwise passing through one or more of the loops 38.The retrieval suture may be used to collapse and retrieve the stent 10,if so desired. For example, the retrieval suture may be pulled like adrawstring to radially collapse the proximal end 14 of the stent 10 tofacilitate removal of the stent 10 from a body lumen.

The stent 10 may have a woven structure, fabricated from a number offilaments or struts 36 forming a tubular wall. In some embodiments, thestent 10 may be knitted or braided with a single filament or strutinterwoven with itself and defining open cells 46 extending through thethickness of the tubular wall of the stent 10. In other embodiments, thestent 10 may be braided with several filaments or struts interwoventogether and defining open cells 46 extending along a length and aroundthe circumference of the tubular wall of the stent 10. The open cells 46may each define an opening from an outer surface of the tubular wall toan inner surface of the tubular wall (e.g., through a thickness thereof)that is free from the filaments or struts 36. Some exemplary stentsincluding braided filaments include the WallFlex®, WALLSTENT®, andPolyflex® stents, made and distributed by Boston Scientific,Corporation. In another embodiment, the stent 10 may be knitted, such asthe Ultraflex™ stents made by Boston Scientific, Corporation. In yetanother embodiment, the stent 10 may be of a knotted type, such thePrecision Colonic™ stents made by Boston Scientific, Corporation. Instill another embodiment, the stent 10 may be a laser cut tubularmember, such as the EPIC™ stents made by Boston Scientific, Corporation.A laser cut tubular member may have an open and/or closed cell geometryincluding one or more interconnected monolithic filaments or strutsdefining open cells 46 therebetween, with the open cells 46 extendingalong a length and around the circumference of the tubular wall. Theopen cells 46 may each define an opening from an outer surface of thetubular wall to an inner surface of the tubular wall (e.g., through athickness thereof) that is free from the interconnected monolithicfilaments or struts. In some instances, an inner and/or outer surface ofthe tubular wall of the stent 10 may be entirely, substantially, orpartially, covered with a polymeric covering or coating 40, as will bedescribed in more detail herein. The covering or coating 40 may extendacross and/or occlude one or more, or a plurality of the cells 46defined by the struts or filaments 36. The covering or coating 40 mayhelp reduce food impaction and/or tumor or tissue ingrowth. In somecases, the stent 10 may be a self-expanding stent (SES), although thisis not required.

In some instances, in the radially expanded configuration, the stent 10may include a first end region 20 proximate the proximal end 14 and asecond end region 22 proximate the second end 16. In some embodiments,the first end region 20 and the second end region 22 may includeretention features or anti-migration flared regions 24, 26 havingenlarged diameters relative to the intermediate portion 18. Theanti-migration flared regions 24, 26, which may be positioned adjacentto the first end 14 and the second end 16 of the stent 10, may beconfigured to engage an interior portion of the walls of the esophagusor other body lumen. In some embodiments, the retention features, orflared regions 24, 26 may have a larger diameter than the cylindricalintermediate region 18 of the stent 10 to prevent the stent 10 frommigrating once placed in the esophagus or other body lumen. It iscontemplated that the transition 28, 30 from the cross-sectional area ofthe intermediate region 18 to the retention features or flared regions24, 26 may be gradual, sloped, or occur in an abrupt step-wise manner,as desired.

In some embodiments, the first anti-migration flared region 24 may havea first outer diameter and the second anti-migration flared region 26may have a second outer diameter. In some instances, the first andsecond outer diameters may be approximately the same, while in otherinstances, the first and second outer diameters may be different. Insome embodiments, the stent 10 may include only one or none of theanti-migration flared regions 24, 26. For example, the first end region20 may include an anti-migration flare 24 while the second end region 22may have an outer diameter similar to the intermediate region 18. It isfurther contemplated that the second end region 22 may include ananti-migration flare 26 while the first end region 20 may have an outerdiameter similar to an outer diameter of the intermediate region 18. Insome embodiments, the stent 10 may have a uniform outer diameter fromthe first end 14 to the second end 16. In some embodiments, the outerdiameter of the intermediate region 18 may be in the range of about 15to 25 millimeters. The outer diameter of the anti-migration flares 24,26 may be in the range of about 20 to 30 millimeters. It is contemplatedthat the outer diameter of the stent 10 may be varied to suit thedesired application.

It is contemplated that the elongated tubular member of the stent 10 canbe made from a number of different materials such as, but not limitedto, metals, metal alloys, shape memory alloys and/or polymers, asdesired, enabling the stent 10 to be expanded into shape when accuratelypositioned within the body. In some instances, the material may beselected to enable the stent 10 to be removed with relative ease aswell. For example, the elongated tubular member of the stent 10 can beformed from alloys such as, but not limited to, nitinol and Elgiloy®.Depending on the material selected for construction, the stent 10 may beself-expanding or require an external force to expand the stent 10. Insome embodiments, composite filaments may be used to make the stentwhich may include, for example, an outer shell or cladding made ofnitinol and a core formed of platinum or other radiopaque material. Itis further contemplated the elongated tubular member of the stent 10 maybe formed from polymers including, but not limited to, polyethyleneterephthalate (PET). In some instances, the filaments of the stent 10,or portions thereof, may be bioabsorbable or biodegradable, while inother instances the filaments of the stent 10, or portions thereof, maybe biostable.

FIG. 2A illustrates a partial perspective view of the illustrative stent10 of FIG. 1 and FIG. 2B illustrates a partial side view of theillustrative stent 10 of FIG. 1 . As described above, the inner and/orouter surface of the tubular wall of the stent 10 may be entirely,substantially, or partially covered with a polymeric covering or coating40. The coating 40 may be silicone, polyurethane or other flexiblepolymeric material. The coating 40 may be applied such that there is anexcess of material or a pocket of material 44 extending between thestruts 36. For example, instead of extending generally taut in the sameplane as the struts 36, the coating 40 may be loose and extend radiallyinward from the struts 36 for a radial distance or height 42 to form avoid. In some instances, the pocket 44 may be generally pyramidalshaped, with four flat converging (e.g., angled) side walls and a flatbottom or base wall. While the pocket 44 is generally illustrated ashaving a rhombus cross-sectional shape similar to a diamond shape of thecells 46 formed by the struts 36, the pocket 44 may take any shapedesired. For instance, in some instances the pocket 44 may have a basewall having a generally arcuate shape, such as a generally sphericalshape with a spherically concave radially outward facing surface and aspherically convex radially inwardly facing surface. The pocket 44 mayform a void between a radially outward surface (e.g., a base surface) ofthe pocket 44 and the circumference of the tubular wall of the stent 10formed by the struts 36.

In some instances, the pockets 44 may be formed using a mandrel and/ormold. For example, a mandrel may be formed having protrusions orrecesses of the desired size and shape of the pockets 44. The struts 36may be wound, braided, woven, or otherwise disposed about the mandrelwith the cells of the tubular wall aligned with the protrusions orrecesses. A sleeve made of, for example, silicone or other polymermaterial, may be disposed over the mandrel and struts 36. The sleeve maybe heated or otherwise molded to the shape of the mandrel to form thecoated stent 10 including the pockets 44 between the struts 36.Alternatively, a polymeric material may be spray or dip coated onto themandrel and struts 36 such that the polymeric material flows over theprotrusions and/or into the recesses of the mandrel. In instances thatthe pockets are formed by protrusions of the mandrel, the pockets maythereafter be inverted to extend radially inward of the tubular wall ofthe stent 10 subsequent to removing the stent 10 from the mandrel.

FIG. 3 illustrates a partial cross-sectional view of the illustrativestent 10 of FIG. 1 deployed in a body lumen 50 having a vessel wall 52.It is contemplated that the coating 40 including the pockets 44 mayincrease frictional forces between the stent 10 and the vessel wall 52while eliminating or substantially reducing tissue ingrowth around thestruts 36 and into the lumen of the stent 10. For example, the coating40 may be a continuous layer which forms an entirety of the innersurface of the stent 10. In other words, the coating 40 may define anentirety of the inner surface of the lumen extending longitudinallythrough the stent 10. Thus, the struts 36 may press into the vessel wall52, but, as the struts 36 are fully covered by the coating 40 and thecoating 40 spans the cells of the tubular wall of the stent 10, tissueingrowth cannot occur around the struts 36 or into the lumen of thestent 10. Said differently, the tissue cannot grow around and surroundthe struts 36. Further, the tissue of the vessel wall 52 may extend intothe void defined by the pockets 44 and radially beyond (e.g., inwardlytowards the lumen 32 of the stent 10) the struts 36 which may helpreduce migration rates of the stent 10. For example, the pockets 44 mayprovide textures or contours which increase friction. In contrast, acoating 40 that is generally in the same plane as the struts 36 or atthe same circumferential position may provide a generally smooth surfacewhich may have lower frictional forces and increased migration rates.

It is contemplated that the volume of tissue that fills the voidsdefined by the pockets 44 may be manipulated by changing a volume of thepockets 44. While the pockets 44 are illustrated as having generallyuniform dimensions (e.g., are all approximately the same size, shape,and/or volume), the pockets 44 need not all have the same dimensions.For example, some pockets 44 may be larger than others. In someembodiments, one or more of the pockets 44 may include an opening 54,such as, but not limited to, an aperture or slit to allow for limitedtissue ingrowth. Limited tissue ingrowth may further reduce migration ofthe stent 10 while still allowing for the removal of the stent 10 withlittle difficulty. Alternatively, or additionally, slits or apertures 54may be provided to allow for a peripheral vessel to drain into the lumen50 (for example, but not limited to, at the ampulla to allow bile toflow into the duodenum) or to create a drainage channel in the stent 10.In some cases, the physician may create the slits or apertures 54 bycutting or punching through the pockets 44.

FIG. 3A illustrates a partial cross-sectional view of a variation of theillustrative stent 10 of FIG. 1 deployed in a body lumen 50 having avessel wall 52. In FIG. 3A, it can be seen that the pockets 44 may beformed having a generally arcuate shape, such as a generally sphericalshape with a spherically concave radially outward facing surface and aspherically convex radially inwardly facing surface.

FIG. 4 illustrates a side view of another illustrative endoluminalimplant 100, such as, but not limited to, a stent. The stent 100 may besimilar in form and function to the stent 10 described herein. In someinstances, the stent 100 may be formed from an elongated tubular member112 defining a tubular wall. While the stent 100 is described asgenerally tubular, it is contemplated that the stent 100 may take anycross-sectional shape desired. The stent 100 may have a first, orproximal end 114, a second, or distal end 116, and an intermediateregion 118 disposed between the first end 114 and the second end 116.The stent 100 may include a lumen 132 extending from a first openingadjacent the first end 114 to a second opening adjacent to the secondend 116 to allow for the passage of food, fluids, etc.

The stent 100 may be expandable from a first radially collapsedconfiguration (not explicitly shown) to a second radially expandedconfiguration. In some cases, the stent 100 may be deployed to aconfiguration between the collapsed configuration and a fully expandedconfiguration. The stent 100 may be structured to extend across astricture and to apply a radially outward pressure to the stricture in alumen to open the lumen and allow for the passage of foods, fluids, air,etc.

In some embodiments, the proximal end 114 of the stent 100 may include aplurality of loops 138. The loops 138 may be configured to receive aretrieval tether or suture (not explicitly shown) interwoventherethrough, or otherwise passing through one or more of the loops 138.The retrieval suture may be used to collapse and retrieve the stent 100,if so desired. For example, the retrieval suture may be pulled like adrawstring to radially collapse the proximal end 114 of the stent 100 tofacilitate removal of the stent 100 from a body lumen.

The stent 100 may have a woven structure, fabricated from a number offilaments or struts 136 forming a tubular wall. In some embodiments, thestent 100 may be knitted or braided with a single filament interwovenwith itself and defining open cells 146 extending along a length andaround the circumference of the tubular wall of the stent 100. The opencells 146 may each define an opening from an outer surface of thetubular wall to an inner surface of the tubular wall (e.g., through athickness thereof) that is free from the filaments or struts 136. Inother embodiments, the stent 100 may be braided with several filamentsor struts interwoven together and defining open cells 146. In anotherembodiment, the stent 100 may be knitted. In yet another embodiment, thestent 100 may be of a knotted type. In still another embodiment, thestent 100 may be a laser cut tubular member. A laser cut tubular membermay have an open and/or closed cell geometry including one or moreinterconnected monolithic filaments or struts defining open cells 146therebetween with the open cells 146 extending along a length and aroundthe circumference of the tubular wall. The open cells 146 may eachdefine an opening from an outer surface of the tubular wall to an innersurface of the tubular wall (e.g., through a thickness thereof) that isfree from the interconnected monolithic filaments or struts. In someinstances, an inner and/or outer surface of the tubular wall of thestent 100 may be entirely, substantially, or partially, covered with apolymeric covering or coating 140, as will be described in more detailherein. The covering or coating 140 may extend across and/or occlude oneor more, or a plurality of the cells 146 defined by the struts orfilaments 136. The covering or coating may help reduce food impactionand/or tumor or tissue ingrowth. In some cases, the stent 100 may be aself-expanding stent (SES), although this is not required.

In some instances, in the radially expanded configuration, the stent 100may include a first end region 120 proximate the proximal end 114 and asecond end region 122 proximate the second end 116. In some embodiments,the first end region 120 and the second end region 122 may includeretention features or anti-migration flared regions 124, 126 havingenlarged diameters relative to the intermediate portion 118. Theanti-migration flared regions 124, 126, which may be positioned adjacentto the first end 114 and the second end 116 of the stent 10, may beconfigured to engage an interior portion of the walls of the esophagusor other body lumen. In some embodiments, the retention features, orflared regions 124, 126 may have a larger diameter than the cylindricalintermediate region 118 of the stent 100 to prevent the stent 100 frommigrating once placed in the esophagus or other body lumen. It iscontemplated that the transition 128, 130 from the cross-sectional areaof the intermediate region 118 to the retention features or flaredregions 124, 126 may be gradual, sloped, or occur in an abrupt step-wisemanner, as desired.

In some embodiments, the first anti-migration flared region 124 may havea first outer diameter and the second anti-migration flared region 126may have a second outer diameter. In some instances, the first andsecond outer diameters may be approximately the same, while in otherinstances, the first and second outer diameters may be different. Insome embodiments, the stent 100 may include only one or none of theanti-migration flared regions 124, 126. For example, the first endregion 120 may include an anti-migration flare 124 while the second endregion 122 may have an outer diameter similar to the intermediate region118. It is further contemplated that the second end region 122 mayinclude an anti-migration flare 126 while the first end region 120 mayhave an outer diameter similar to an outer diameter of the intermediateregion 118. In some embodiments, the stent 100 may have a uniform outerdiameter from the first end 114 to the second end 116. In someembodiments, the outer diameter of the intermediate region 118 may be inthe range of about 15 to 25 millimeters. The outer diameter of theanti-migration flares 124, 126 may be in the range of about 20 to 30millimeters. It is contemplated that the outer diameter of the stent 100may be varied to suit the desired application.

It is contemplated that the elongated tubular member of the stent 100can be made from a number of different materials such as, but notlimited to, metals, metal alloys, shape memory alloys and/or polymers,as desired, enabling the stent 100 to be expanded into shape whenaccurately positioned within the body. In some instances, the materialmay be selected to enable the stent 100 to be removed with relative easeas well. For example, the elongated tubular member of the stent 100 canbe formed from alloys such as, but not limited to, nitinol and Elgiloy®.Depending on the material selected for construction, the stent 100 maybe self-expanding or require an external force to expand the stent 10.In some embodiments, composite filaments may be used to make the stentwhich may include, for example, an outer shell or cladding made ofnitinol and a core formed of platinum or other radiopaque material. Itis further contemplated the elongated tubular member of the stent 100may be formed from polymers including, but not limited to, polyethyleneterephthalate (PET). In some instances, the filaments of the stent 10,or portions thereof, may be bioabsorbable or biodegradable, while inother instances the filaments of the stent 10, or portions thereof, maybe biostable.

FIG. 5A illustrates a partial perspective view of the illustrative stent100 of FIG. 4 and FIG. 5B illustrates a partial side view of theillustrative stent 100 of FIG. 4 . As described above, the inner and/orouter surface of the tubular wall of the stent 100 may be entirely,substantially, or partially covered with a polymeric covering or coating140. The coating 140 may be silicone, polyurethane or other flexiblepolymeric material. The coating 140 may be applied such that there is anexcess of material or a pocket of material 144 extending between thestruts 136. For example, instead of extending generally taut in the sameplane as the struts 136, the coating 140 may be loose and extendradially inward from the struts 136 for a radial distance or height 42to form a void. In some instances, the pocket 144 may be generallypyramidal shaped, with four flat converging (e.g., angled) side wallsand a flat bottom or base wall. While the pocket 144 is generallyillustrated as having a rhombus cross-sectional shape similar to adiamond shape of the cells 146 formed by the struts 136, the pocket 144may take any shape desired. For instance, in some instances the pocket144 may have a base wall having a generally arcuate shape, such as agenerally spherical shape with a spherically concave radially outwardfacing surface and a spherically convex radially inwardly facingsurface. The pocket 144 may form a void between a radially outwardsurface (e.g., a base surface) of the pocket 144 and the circumferenceof the tubular wall of the stent 100 formed by the struts 136.

In some cases, the pocket 144 may be divided or split using a partitionor wall 148. It is contemplated that the partition or wall 148 may beformed from the same material as or a different material from thecoating 140, as desired. Each partition or wall 148 may extend acrossthe pocket 144 to transect the void formed by the pocket 144. Forexample, each partition or wall 148 may extend entirely across the voidfrom a first side of the pocket 144 to a second side of the pocket 144in which it is situated and radially outward from a bottom surfacethereof. For example, each partition or wall 148 may extend entirelyacross the void from a first side wall of the pocket 144 to a secondside wall of the pocket 144 in which it is situated and radially outwardfrom a base wall thereof. In other instances, each partition or wall mayextend only across a portion of the void and have one or more endsspaced away from the side walls of the pocket 144. The partitions orwalls 148 may be formed as a single monolithic structure with thecoating 140 and pockets 144. In other embodiments, the partitions orwalls 148 may be formed as a separate structure and subsequently securedwithin the pocket 144 using, for example, heat and/or adhesives. In somecases, the partition or wall 148 may be configured to extend betweenopposing cross-over points 160 of intersecting struts 136. For instance,in some instances, the partition or wall 148 may extend from a firstcorner to an opposite corner of a pyramidal shaped pocket 144. This maydivide the void defined by the pocket 144 in approximately half. In somecases, the partitions or walls 148 may extend generally orthogonal to acentral longitudinal axis 162 (see, for example, FIG. 4 ) of the stent100. However, this is not required. In some embodiments, the partitionsor walls 148 may extend generally parallel to the central longitudinalaxis 162 of the stent 100. In yet other embodiments, the partitions orwalls 148 may extend at an oblique angle relative to the centrallongitudinal axis 162. For example, a first end of the partition or wall148 may be positioned between two adjacent cross-over points 160 and asecond end of the same partition or wall 148 may be positioned betweentwo adjacent cross-over points 160 on an opposite side of the cell 146.Thus, the partition or wall 148 may extend from a first corner to anopposite corner of a pyramidal shaped pocket 144. In some cases, thepartitions or walls 148 may be oriented in differing directions. Forexample, some partitions or walls 148 may extend generally perpendicularto the central longitudinal axis 162, some partitions or walls 148 mayextend generally parallel to the central longitudinal axis 162, and/orsome partitions or walls 148 may extend at an oblique angle relative tothe longitudinal axis 162, or any combination thereof. It is furthercontemplated that the partition or wall 148 may not divide the pocket144 uniformly. In some embodiments, one or more pockets 144 may includemore than one wall 148, for example.

The partitions or walls 148 may have first and second opposing sidesurfaces facing first and second divided regions of the void,respectively. The partitions or walls 148 may have a base joined to thebase wall of the pocket 144, and an opposite free end extending radiallyoutward therefrom.

In some instances, the pockets 144 and/or partitions or walls 148 may beformed using a mandrel and/or mold. For example, a mandrel may be formedhaving recesses of the desired size and shape of the pockets 144 withprotrusions extending outward from the recesses to form the partitionsor walls 148. The struts 136 may be wound, braided, woven, or otherwisedisposed about the mandrel with the cells of the tubular wall alignedwith the recesses. A sleeve made of, for example, silicone or otherpolymer material, may be disposed over the mandrel and struts 136. Thesleeve may be heated or otherwise molded to the shape of the mandrel toform the coated stent 100 including the pockets 144 and partitions orwalls 148 between the struts 136. Alternatively, a polymeric materialmay be spray or dip coated onto the mandrel and struts 136 such that thepolymeric material flows over the protrusions and/or into the recessesof the mandrel.

FIG. 6 illustrates a partial cross-sectional view of the illustrativestent 100 of FIG. 4 deployed in a body lumen 150 having a tissue wall152. It is contemplated that the coating 140 including the pockets 144and partitions or walls 148 may increase frictional forces between thestent 100 and the tissue wall 152 while eliminating or substantiallyreducing tissue ingrowth around the struts 136 and into the lumen of thestent 100. For example, the coating 140 may be a continuous layer whichforms an entirety of the inner surface of the stent 100. In other words,the coating 140 may define an entirety of the inner surface of the lumenextending longitudinally through the stent 100. Thus, the struts 136 maypress into the tissue wall 152, but, as the struts 136 are fully coveredby the coating 140 and the coating spans the cells of the tubular wallof the stent 100, tissue ingrowth cannot occur around the struts 136 orinto the lumen of the stent 100. Said differently, the tissue cannotgrow around and surround the struts 136. Further, the tissue of thetissue wall 152 may extend into the pockets 144 and, sometimes radiallybeyond (e.g., inwardly towards the lumen 132 of the stent 100) thestruts 136 which may help reduce migration rates of the stent 10. Forexample, the pockets 144 may provide textures or contours which increasefriction. In contrast, a coating 140 that is generally in the same planeas the struts 136 or at the same circumferential position may provide agenerally smooth surface which may have lower frictional forces andincreased migration rates. It is contemplated that the partitions orwalls 148 may increase the surface area of the coating 140 to furtherincrease the friction properties of the stent 100. It is contemplatedthat width 164 and/or height 142 of the partition or wall 148 may bevaried to increase or decrease the surface area of the coating 140. Forexample, while the stent 100 is generally illustrated as the walls 148having a height 142 approximately equal to a height of the strut 136with the coating 140 disposed thereon, the height 142 may be greaterthan or less than the height of the strut 136 with the coating 140disposed thereon. It is further contemplated that the partitions orwalls 148 each have the same height 142. It is contemplated that theheight 142 may vary uniformly, non-uniformly, in a patterned arrangementor eccentrically about the length and/or circumference of the stent 100.While the partition or wall 148 is illustrated as having a generallycubic rectangular shape, other shapes may be used, such as, but notlimited, hemispherical, conical, pyramidal, etc.

It is contemplated that the volume of tissue that fills the voids of thepockets 144 may be manipulated by changing a volume of the pockets 144and/or the size of the walls partitions or 148. While the pockets 144and partitions or walls 148 are each illustrated as having generallyuniform dimensions (e.g., are all approximately the same size, shape,and/or volume), the pockets 144 and/or partitions or walls 148 need notall have the same dimensions. For example, some pockets 144 and/orpartitions or walls 148 may be larger than others. In some embodiments,one or more of the pockets 144 may include an opening, such as, but notlimited to, an aperture or slit to allow for limited tissue ingrowth.Limited tissue ingrowth may further reduce migration of the stent 100while still allowing for the removal of the stent 100 with littledifficulty. Alternatively, or additionally, slits or apertures may beprovided to allow for a peripheral vessel to drain into the lumen 150 orto create a drainage channel in the stent 100. In some cases, thephysician may create the slits or apertures by cutting or punchingthrough the pockets 144.

FIG. 6A illustrates a partial cross-sectional view of a variation of theillustrative stent 100 of FIG. 4 deployed in a body lumen 50 having avessel wall 52. In FIG. 6A, it can be seen that the pockets 144 may beformed having a generally arcuate shape, such as a generally sphericalshape with a spherically concave radially outward facing surface and aspherically convex radially inwardly facing surface. The partitions orwalls 148 may extend radially outward from the spherically concaveoutward facing surface.

The stents, delivery systems, and the various components thereof, may bemade from a metal, metal alloy, polymer (some examples of which aredisclosed below), a metal-polymer composite, ceramics, combinationsthereof, and the like, or other suitable material. Some examples ofsuitable metals and metal alloys include stainless steel, such as 304V,304L, and 316LV stainless steel; mild steel; nickel-titanium alloy suchas linear-elastic and/or super-elastic nitinol; other nickel alloys suchas nickel-chromium-molybdenum alloys, nickel-copper alloys,nickel-cobalt-chromium-molybdenum alloys, nickel-molybdenum alloys,other nickel-chromium alloys, other nickel-molybdenum alloys, othernickel-cobalt alloys, other nickel-iron alloys, other nickel-copperalloys, other nickel-tungsten or tungsten alloys, and the like;cobalt-chromium alloys; cobalt-chromium-molybdenum alloys; platinumenriched stainless steel; titanium; combinations thereof; and the like;or any other suitable material.

Some examples of suitable polymers for the stents or delivery systemsmay include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene(ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, forexample, DELRIN® available from DuPont), polyether block ester,polyurethane (for example, Polyurethane polypropylene (PP),polyvinylchloride (PVC), polyether-ester (for example, ARNITEL®available from DSM Engineering Plastics), ether or ester basedcopolymers (for example, butylene/poly(alkylene ether) phthalate and/orother polyester elastomers such as HYTREL® available from DuPont),polyamide (for example, DURETHAN® available from Bayer or CRISTAMID®available from Elf Atochem), elastomeric polyamides, blockpolyamide/ethers, polyether block amide (PEBA, for example availableunder the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA),silicones, polyethylene (PE), MARLEX® high-density polyethylene, MARLEX®low-density polyethylene, linear low density polyethylene (for exampleREXELL®), polyester, polybutylene terephthalate (PBT), polyethyleneterephthalate (PET), polytrimethylene terephthalate, polyethylenenaphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI),polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide(PPO), poly paraphenylene terephthalamide (for example, KEVLAR®),polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMSAmerican Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinylalcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC),poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitablematerials, or mixtures, combinations, copolymers thereof, polymer/metalcomposites, and the like.

In at least some embodiments, portions or all of the stents or deliverysystems may also be doped with, made of, or otherwise include aradiopaque material. Radiopaque materials are generally understood to bematerials which are opaque to RF energy in the wavelength range spanningx-ray to gamma-ray (at thicknesses of <0.005″). These materials arecapable of producing a relatively dark image on a fluoroscopy screenrelative to the light image that non-radiopaque materials such as tissueproduce. This relatively bright image aids the user of the stents ordelivery systems in determining its location. Some examples ofradiopaque materials can include, but are not limited to, gold,platinum, palladium, tantalum, tungsten alloy, polymer material loadedwith a radiopaque filler, and the like. Additionally, other radiopaquemarker bands and/or coils may also be incorporated into the design ofthe stents or delivery systems to achieve the same result.

It should be understood that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of steps without exceeding the scope of thedisclosure. This may include, to the extent that it is appropriate, theuse of any of the features of one example embodiment being used in otherembodiments. The invention's scope is, of course, defined in thelanguage in which the appended claims are expressed.

What is claimed is:
 1. A stent, the stent comprising: an elongatedtubular member comprising at least one strut forming a tubular wallhaving a plurality of cells extending through a thickness of the tubularwall, the elongated tubular member configured to move between a radiallycollapsed configuration and a radially expanded configuration; and acoating disposed on the elongated tubular member and spanning theplurality of cells, the coating forming a pocket within at least some ofthe plurality of cells and extending radially inward of the tubular wallto define a void; wherein the pockets are truncated pyramidal shaped,with four converging side walls and a radially inward base wallintersecting each of the four converging side walls; wherein a radiallyoutward facing surface of the base wall is spaced radially inwardly of aradially innermost extent of the tubular wall.
 2. The stent of claim 1,further comprising a partition positioned within at least some of thepockets, each partition extending radially outward from the radiallyoutward facing surface of the base wall of its respective pocket andtransecting the void.
 3. The stent of claim 2, wherein at least some ofthe partitions extend generally perpendicular to a central longitudinalaxis of the elongated tubular member.
 4. The stent of claim 2, whereinat least some of the partitions extend generally parallel to a centrallongitudinal axis of the elongated tubular member.
 5. The stent of claim2, wherein at least some of the partitions extend at an oblique anglerelative to a central longitudinal axis of the elongated tubular member.6. The stent of claim 2, wherein a height of the partitions isapproximately equal to a height of the at least one strut having thecoating disposed thereon.
 7. The stent of claim 2, wherein the at leastone strut forms a plurality of cross-over points.
 8. The stent of claim7, wherein at least some of the partitions extend between adjacentcross-over points.
 9. The stent of claim 2, wherein at least one pocketincludes two or more partitions.
 10. The stent of claim 2, wherein thecoating and the partitions are formed as a single monolithic structure.11. The stent of claim 1, wherein the coating defines an entirety of asurface of a lumen extending longitudinally through the stent.
 12. Thestent of claim 1, wherein at least some of the pockets include anaperture formed therethrough.
 13. A stent, the stent comprising: anelongated tubular member comprising at least one strut forming a tubularwall having a plurality of cells extending through a thickness of thetubular wall, the elongated tubular member configured to move between aradially collapsed configuration and a radially expanded configuration;and a coating disposed on the elongated tubular member and spanning theplurality of cells, the coating forming a pocket within at least some ofthe plurality of cells and extending radially inward of the tubular wallto define a void; wherein the pockets have a rhombus shapedcross-section, with four flat side walls intersecting a base wall;wherein a radially outward facing surface of the base wall is spacedradially inwardly of a radially innermost extent of the tubular wall.14. The stent of claim 13, further comprising a partition positionedwithin at least some of the pockets, each partition extending radiallyoutward from the radially outward facing surface of the base wall of itsrespective pocket and transecting the void.
 15. The stent of claim 13,wherein the coating and the partitions are formed as a single monolithicstructure.
 16. The stent of claim 13, wherein at least some of thepockets include an aperture formed therethrough.
 17. A stent, the stentcomprising: an elongated tubular member comprising at least one strutforming a tubular wall having a plurality of cells extending through athickness of the tubular wall, each of the plurality of cells having across-sectional shape, the elongated tubular member configured to movebetween a radially collapsed configuration and a radially expandedconfiguration; and a coating disposed on the elongated tubular memberand spanning the plurality of cells, the coating forming a pocket withinat least some of the plurality of cells and extending radially inward ofthe tubular wall to define a void; wherein the pockets each have across-sectional shape that is the same as the cross-sectional shape ofthe plurality of cells, the pockets each including four converging sidewalls and a radially inward base wall intersecting each of the fourconverging side walls; wherein a radially outward facing surface of thebase wall is spaced radially inwardly of a radially innermost extent ofthe tubular wall.
 18. The stent of claim 17, wherein the cross-sectionalshape of the plurality of cells is a diamond shape.
 19. The stent ofclaim 17, further comprising a partition positioned within at least someof the pockets, each partition extending radially outward from theradially outward facing surface of the base wall of its respectivepocket and transecting the void.
 20. The stent of claim 17, wherein atleast some of the pockets include an aperture formed therethrough.